Doi / Marinescu / Kurokawa Advances in CMP Polishing Technologies

1. Auflage 2011
ISBN: 978-1-4377-7860-1
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 328 Seiten

CMP and polishing are the most precise processes used to finish the surfaces of mechanical and electronic or semiconductor components. Advances in CMP/Polishing Technologies for Manufacture of Electronic Devices presents the latest developments and technological innovations in the field - making cutting-edge R&D accessible to the wider engineering community. Most of the applications of these processes are kept as confidential as possible (proprietary information), and specific details are not seen in professional or technical journals and magazines. This book makes these processes and applications accessible to a wider industrial and academic audience. Building on the fundamentals of tribology - the science of friction, wear and lubrication - the authors explore the practical applications of CMP and polishing across various market sectors. Due to the high pace of development of the electronics and semiconductors industry, many of the presented processes and applications come from these industries. - Demystifies scientific developments and technological innovations, opening them up for new applications and process improvements in the semiconductor industry and other areas of precision engineering - Explores stock removal mechanisms in CMP and polishing, and the challenges involved in predicting the outcomes of abrasive processes in high-precision environments - The authors bring together the latest innovations and research from the USA and Japan

Autoren/Hrsg.

Doi, Toshiro

Marinescu, Ioan D.

Kurokawa, Syuhei

Leseproben

Chapter 2. Details of the Fabrication Process for Devices with a Silicon Crystal Substrate

Silicon single crystals are used as semiconductor devices primarily because it is easy to form silica (SiO2) films on the crystal surface. The history of the development of semiconductors, from the first integrated circuits to the situation today is discussed. Metal oxide semiconductors (MOS), complementary MOS (CMOS) and large scale integrated circuits (LSIs) are considered. An overview is given of process integration technology, where a given integrated circuit is made by assembling different unit elements. As process integration becomes more complicated, the requirement for the separation of process integration becomes greater. With the introduction of chemical mechanical polishing (CMP), almost ideal planarization can be realized and the process integration can be separated into upper and lower parts. Element isolation and multi-interconnection are discussed as an example of how planarization CMP technology is used in a device process.

Keywords

Semiconductor; silicon single crystal; integrated circuit; process integration; chemical mechanical polishing; CMP

The groundbreaking invention of the transistor marked the beginning of the information technology era in the twentieth century. It is said that the development of the transistor by Shockley et al. at the Bell Institute in the US originated from a phenomenon in which an electric current changed according to the position of the electrode, when one more needle was added to a germanium wave inspector to make it a tripole. The word transistor is a combination of the words transfer and resistor, and suggests amplification of the electric current.

After the advent of the transistor, the progress of solid electronic devices slowed, until in 1959 a functional element that formed the basis of the IC (Integrated Circuit) was designed: a condenser and a resistor were used in a transistor on a single crystal substrate made of Ge (germanium) and Si (silicon) with interconnections assembled together and integrated. Silicon in particular was supported by high-quality crystal growth technology and has contributed to today’s ultra-LSI.

In this chapter, the fabrication process for a device with a silicon substrate is introduced. The development process is discussed, and an overview is given of current and future challenges for device process technology.

2.1. History of Semiconductor Devices and their Types

Silicon single crystals are used as semiconductor devices primarily because it is easy to form SiO2 (oxidation) films on the crystal surface, which have excellent stability and insulation properties. As this technology of utilizing oxidizing film has progressed, silicon IC technology has developed. This technology, called the Planar Process, was initially developed by Noyce, of Fairchild Co. in the US (a founder of the current Intel) in 1959, and was an extremely important technology that opened the way for IC production, so marking the starting point of the current semiconductor IC. Figure 2.1 shows the basic scheme of the formation of a pn junction by lithography and the planar process. This opens windows in SiO2 films which have been formed on a semiconductor silicon substrate, and, through these windows, impurities (boron in this case) are injected and diffused. Because SiO2 films are insulators, electrical conductive films (for example an Al film) can be interconnected.

Figure 2.1 Basic scheme showing the formation of a pn junction with lithography and the Planar Process

The first IC was reported in a patent applied for by Jack Kilby of Texas Instrument Co. in 1959. He produced a basic IC, consisting of only two transistors and several resistors on Ge crystals; thin lead was used as interconnectors. This technology was combined with the above-mentioned planar technology and has since progressed into current ICs. J. Kilby was awarded the Nobel Prize in Physics for his “contribution to the invention of the IC” in 2000.

The IC that emerged in 1963 made a debut as a MOS (Metal Oxide Semiconductor) or CMOS (Complementary MOS, MOS transistor having both p/n channels) device (Figure 2.2). Integration technology was enhanced in 1967 when the announcement of CMOS logics (by RCA Co.) was made, and in 1971 Intel developed a microprocessor that could deal with 1kbit memory DRAM (Dynamic Random Access Memory) and 4 bit data. This opened the door to LSIs (Large Scale Integrated Circuits). ICs gradually came to have several hundred elements and, around 1970, developed into an LSI, having several thousand elements.

Figure 2.2 Basic structure of CMOS device

At this time, a magnetic memory was used as the main memory in a computer, but DRAM invented later, replaced it. As early as 1976, 64k DRAM was developed; 1982, 1M emerged, and the era of Mega began. In 1971, a 4-bit microprocessor was developed, increasing to an 8-bit MPU (Micro Processing Unit) in 1975, and, in 1981, to a 16-bit MPU. LSI was a tremendous breakthrough for the IC, and fierce competition in development between Japan and the US took place in the late 1970s, symbolized by the 64kbit memory launched into the US market by Japanese companies. Moore‘s Law, advocated by Dr. Gordon Moore in his paper in 1965, describes a long-term trend of micro-processors. The paper indicated that the number of transistors on an integrated circuit would double every 2 years. He left Fairchild and founded what is currently Intel, with Noyce. This declaration soon became the goal of the whole semiconductor industry and formed the basis for a road map for a semiconductor technology of SEMATECH in the US.

Meanwhile the LSI cooperative research committee was set up in Japan in 1976, and both public and private sectors worked together for four years to develop an LSI with 1µm machining technology. In the 1980s, 64kbit, 256kbit and 1Mbit memories occupied more than half of the market, showing the lead gained by Japanese technology, which had excellent mass productivity and reliability.

Figure 2.3 shows the types and progress of IC, classified by its basic integration. Figure 2.4 shows a schematic picture of the development process of a CMOS device, as the basic circuit of an ultra-LSI. Thirty years after the introduction of the LSI in 1970, processor ability has increased by an amazing 1 million times. DRAM has developed just as quickly, from k- to Mbit and then, finally, to Gbit. Factors contributing to Moore’s Law have been microprocess technology, circuit technology and the technology of new materials. Various innovative technologies have made it possible to achieve line widths down to 40µm for today’s LSIs, and 32µm or less is expected to be achievable after 2013.

Figure 2.3 Progress of CMOS devices

Figure 2.4 Device trend having MOS at the center and the progress

2.2. Semiconductor Device Process Technology and current Situation

Process integration technology makes a given IC by assembling elements (unit or elementary), as seen in Table 2.1. The reference (name) differs between makers and includes consistent process, integrated process, total process, through process and integration process.

Table 2.1 Process Integration Technology by Assembling Element Processes

• Integrated Circuit Substrate

– Single crystal wafer base plate: Intrinsic Gettering – Epitaxial grown – Homo: Si grown on Si – Hetero: a-Si, SiC, Si-Ge – SOI – Fusion Recrystallization – Solid phase grown – SIMOX (Separation by Implanted Oxygen) – Pasting wafer: Direct connection, organic Film integration

• Lithography

– Light transfer process: Same size projection, shrinking projection (stepper, scanner) – Electron beam portrayal: point beam, fairing beam – X-ray portrayal: Same size, Shrinking

• Etching

– Solution technique – Dry etching – RIE (Reactive Ion Etching) – Ion milling – UV exposure, Usher – CMP (Chemical Mechanical Polishing) – Lift off

• Insulating Film Formation

– Oxidation – CVD (Chemical Vapor Deposition) – Sputter – Chemical anode

• Junction Formation

– Ion milling – Solid diffusion – Silicide: Face of Si base plate –...